1. Field of the Invention
The present invention relates to a cylinder identifying apparatus for an internal-combustion engine which identifies a cylinder from a signal from one system of signal generating means.
2. Description of Related Art
In order to control the ignition timing and the fuel injection quantity of an internal-combustion engine, a signal synchronized with the rotation of the engine is used. This signal generator normally detects the rotation of the crank shaft of the engine or a cam shaft which rotates in synchronization with the crank shaft at half of the number of revolutions thereof.
An example of such signal generating means is shown in FIGS. 4 and 5. A window 3 is provided at a place corresponding to a desired detection angle on a rotary disk. Referring to FIG. 4, numeral 1 denotes a cam shaft which rotates in synchronization with an engine (not shown); numeral 2 denotes a rotary disk mounted to the cam shaft 1; numeral 4 denotes a light emitting diode; and numeral 5 denotes a photodiode which receives the output light from the light emitting diode 4 through the window 3 provided on the rotary disk 2.
In FIG. 5, numeral 6 denotes an amplifier circuit, connected to the photodiode 5, for amplifying an output signal from the photodiode 5; and numeral 7 denotes an output transistor for an open collector connected to the amplifier circuit 6. Such a signal as shown in FIG. 7 is outputted from the signal generating means (See FIG. 6). A crank angle reference signal (SGT) shown in FIG. 7 reverses at a predetermined crank angle for each cylinder, and is used as a reference signal for the crank angle.
In order to identify a reference position corresponding to each cylinder, a signal for cylinder identification is caused to be additionally outputted immediately after a reference position signal for cylinder #1 occurs. It is described also in Japanese Patent Publication No. 7-58058 that an occurrence interval between these signals is measured to detect timing of a specified cylinder (cylinder #3 in FIG. 7) on the basis of a ratio of occurrence interval between two continuous sections, and that after the specified cylinder is identified, other cylinders will be identified in order on the basis thereof.
The addition of an identification signal as described above enables a specified cylinder to be identified, and control for each cylinder can be performed by identifying other cylinders in order. In this respect, an output signal from rotation signal generating means 8 is inputted into a microcomputer 10 through an interface circuit 9 as shown in FIG. 6 to control the ignition, the fuel injection and the like of the cylinder which has been identified in synchronization with such input signal.
If, however, a starting switch is turned off by an operator's failure or the like at the time of starting, during compression stroke (at crank angle position before top dead center) before the internal-combustion engine completely starts, the internal-combustion engine may reverse to stop.
In this case, since it is not capable of recognizing a reversed state, the microcomputer 10 erroneously controls in response to a crank angle reference signal (SGT) detected at the time of the reverse, thus possibly damaging the internal-combustion engine.
For example, when reversed at time t2 (during compression stroke) immediately after passing the first reference crank angle B75.degree. of cylinder #4 forward as shown in FIG. 8, the microcomputer 10 erroneously recognizes the signal at the first reference crank angle B75.degree. of the cylinder #4 at time t3 as a signal at a second reference crank angle B5.degree. of the cylinder #4 which has been passed reversed, and also recognizes the signal at the first reference crank angle B75.degree. of the same cylinder #4 at time t4 as a signal at the first reference crank angle B75.degree. of the next cylinder #2 to erroneously control the cylinder #2.
Also, when reverse occurs before the termination of cylinder identification (before an additional signal for cylinder identification is specified), the microcomputer 10 recognizes a normal cylinder signal as an additional signal for cylinder identification on the basis of a rate of a signal occurrence interval at the reversed cylinder to a signal occurrence interval at the next cylinder to control an erroneous cylinder.